To print an image obtained by a digital camera, required is a procedure to transfer image data via a serial interface such as an RS-232C interface or a memory card to a personal computer, then, to perform processing corresponding to a print format of a printer on the image data in the personal computer, then sent print data via a parallel interface such as a Centronics interface or a serial interface such as a USB (Universal Serial Bus) interface to the printer, and print an image by the printer.
If a user of the digital camera has a personal computer, the user generally performs image processing by using necessary application software and performs printing by a printer connected to the personal computer. However, if the user does not have a personal computer, as the user has no means for printing the image obtained by the digital camera, the user connects the digital camera to a video terminal of a home television set and only watches the obtained image on the television screen.
A printer system in the form of video printer has been provided to such user. The video printer directly transfers image data from a digital camera to a printer by using a serial interface of its original specification, an infrared interface, a memory card or the like without a personal computer, performs image processing in the printer, and performs printing. Note that printing by transferring image data to a printer without personal computer is generally called “direct printing”.
As the print system to perform direct printing does not have a personal computer, it is necessary to convert JPEG (Joint Photographic Experts Group) compressed image data to print data in any device (digital camera or printer). Accordingly, the processing speed is greatly influenced by data processing performance of the device.
For example, since a general printer is constructed on the precondition that a personal computer performs processing to convert image data to printer-specific print data, the printer has no high-level data processing performance for the sake of cost-priority specification.
In the direct-print printer, to improve the processing performance to convert image data to print data, it is necessary to expand functions by e.g. increasing the processing speed of CPU, distribution of processing by using plural CPU's, and increasing in data size to be converted at once by increasing in internal memory capacity.
Further, an image supply device (e.g. digital camera) corresponding to the direct printing may be provided with a print data generation function. Although a general digital camera or the like has fully high processing performance of image data compression, decompression and display and the like, it does not have high performance of print data generation.
That is, the image supply device and printing device corresponding to the direct printing provide a series of processing functions, however, any of the devices cannot be expected to have high processing performance. Accordingly, printing time is longer in comparison with the system having the personal computer.